text: """Hex string to byte array.
  
  From hex string _s of _2n digits, build the equivalent array _a of _n bytes.
  Each pair of hexadecimal characters (16 possible values per digit) is decoded into one byte (256 possible values).
  
  Source: programming-idioms.org
  """
  
  # Implementation author: Oldboy
  # Created on 2019-02-11T20:01:36.48212Z
  # Last modified on 2019-03-26T21:23:37.827454Z
  # Version 2
  
  a = bytearray.fromhex(s)
  